Glow-discharge lamp



Jan'G, `1931. E. A. LEDERER GLOW DISCHARGE LAMP Filed July 9, 1924 2 Sheets-Sheet 1 INVENTOR -1w/wmv' ,4. socken Jan 6, 1931. E A, LEDERER 1,787,689

GLOW DISCHARGE LAMP Fi1ed`Ju1y9, .1924 2 Sheots-jSheet 2 I-'l c. 4

INVENTOR ERNasT A. Lsoznel ATTORNEY Patented Jan. 6, 1931 UNITED STATES PATENT OFFICE- ERNEST ANTON LEDERER, 0F BLOOMFIELD, NEW JERSEY, ASSIGNOR TO 'WESTINGHOUSE .LAMP COMPANY, A CORPORATII'ION .0F PENNSYLVANIA Grow-DISCHARGE LAMP Application led July 9,

This invention relates to glow-discharge' lamps and more' particularly to lamps for converting electrical variations into variations in light.

This lamp is particularl ada ted for use in the electrical transmission o either still or moving pictures by wire or by wireless and for recording sound phctographically but it is not so limited.

The electrical transmission of pictures is accomplished in substantially all of the known systems by converting the light intensity of small areas of said picture successively into electrical variations and. transmitting said electrical variations by Wire or wireless to the receiving station where apparatus operating in synchronism with the transmitting apparatus recouverts the electrical variations into light modulations and projects -such light modulations progressively over a screen or a sensitized surface, as a film or plate, to reproduce the picture.

The variations in the current strength of the transmitted impulses may be produced in different Ways. They may, for instance, be obtained by the passage of a mechanical pointer over specially prepared metal picture having a cylindrical surface or they may be produced by introducing a pair of rotatable ring prisms between an ordinary object or picture to progessively direct the light from small areas of the object or picture upon a light sensitive cell. The light sensitive cell translates the variations in light intensity of the diEerent parts of the picture intovariations in current strength and these latter variations are transmitted to a receiving station by wires or by wireless.

In all of these -systems it is desirable that the apparatus for reconverting these electrical variations into light modulations should employ a concentrated light source, of unvarying color, the intensity of which, may be instantly and accurately varied in accordance with the variations in the received impulses.

It is desirable that the light source be concentrated in order that it may be projected .t any one instant on a relatively small area i0 of the sensitized surface; it must be of con- 1924. Serial No. 724,991.

stant color since the photographic medium is differently affected b light of different wave lengths; it must be ree from inertia to permit rapid transmission of the picture and to prevent distortion thereof; it must be capable of being varied accurately in accordance -with the variations .in the transmitted impulses to produce the proper tone graduations in the reproduced picture and it must be intense or brilliant to reduce the necessary time of exposure.

One of the objects of this invention is to provide a light source of this character.

Another object is to provide a lamp in which small current variations impressed thereon will produce relatively large variations in the light intensity of the lamp.

Another object is to provide a glow-discharge lamp having a low starting potential and a high eiiiciency.

Another object 1s to provide a glow-discharge lamp operable on ordinary commer-l cial lighting circuits.

Another object is to provide a discharge lamp in which the light emitting column is conned to a relatively small cross sectional area.

Another :object of the invention is to prevent undesirable and uncontrolled discharges in a lamp of this character.

Another object is to provide a discharge device capable of rectifying alternating cur-yy rents.

Other objects and advantages will hereinafter appear. 4

In accordance with the preferred embodiment of this invention, the discharge lamp is provided with three electrodes, two of which are preferably arranged relatively close together and serve to ionizev a gaseous medium contained within .the lamp s o as to permit a. low potential discharge between one or both of said electrodes' and the third electrode. Preferably, the gaseous medium is a rare gas as neon or helium at' a low pressure by which the current consumption is decreased and the starting potential made relatively low: However, a mixture of rare gases with or without other gaseous chemical compounds or vapors may be used, to modify the color for photographic purposes.

The cathode fall and consequently 'the potential drop between the electrodes may be further reduced by coating the electrodes with an alkali metal as potassium, sodium, rubidium, caesium, lithium, or alloys thereof, preferably vaporized on the electrodes after they are sealed into the lamp.

The ionizing electrodes may be enclosed in a chamber having a constricted discharge passage communicating with the third electrode and in which a positive glow is produced and concentrated into a column of small cross sectional area.

The ionizing electrodes may be connected in one circuit and the light-producing electrodes in another circuit, either of which may be varied to control the intensity of the light as will hereinafter more fully ap iear.

The transmitted impulses may e received by any of the usual radio receiving apparatus and impressed upon the electrodes of the lamp to produce light modulations corresponding to the transmitted impulses.

If it is desiredto record sound photographically, the sound may be impressed by a microphone or' `similar devicedirectly upon a circuit in which `the-electrodes of the lamp are connectedbr through suitable amplifying means, and the light variations thus prodiced'- p rojected on a continuously moving In order" that theinvention may be more fully understood, reference is had to the accompanying drawings in which, 1 Fig. 1 is a sectional view of a discharge Fig. 2 is a sectional view of another form of discharge lamp;

Figs. 3, 4 and 5 are diagram arrangements which may be employed for operating the discharge lamp; and,

Fig. 6 is a diagram arrangement utilizing the discharge device as a rectiier.

The discharge lamp shown in Fig. 1 comprises an` envelope 1 containing a rare gas as neon or helium preferably at a relatively low pressure, a tubular chamber 2 in which concentric electrodes 3 and 4 are arranged and a third electrode 5 located outside of the chamber 2.

The electrode 3 is composed of a wire or ribbon of metal having a low cathode drop,

as aluminum wound spirally about the leads;z

ing-in conductor 6. The electrode 4 is in the form of a metallic tube preferably of aluminum, surrounding the electrode 3 and of such size as to have its surface arranged relatively closeto the inner electrode whereby a compact structure is obtained and a glow-discharge produced therebetween at relatively low voltages. The electrode 4 is supported by the leading-in wire 7. The leading-in wires 6 and 7 are contained within tubular legs 8 which latter-form extensions -of the chamber 2 and are fused t'o the reentrant stem 9 of the lamp. The leading-in wires are sealed in the stem 9.

The upper portion 10 of the chamber 2 has an open end 11 and is reduced in cross section to produce a constricted discharge passage between the outside electrode 5 and the electrodes 3 and 4. The electrode 5 comprises a disc of metal, as aluminum, having a central opening 12, supported by the reduced portion of the chamber 2 through a pair of cli s 13 to which the leading-in wire 14l is suita l'y secured, as by welding.

In the operation of this lamp, a sufficient potential is applied between the electrodes 3 and 4 to cause a glow-discharge therebetween which ionizes the gas within the chamber and reduces the starting potential of the main discharge produced between the electrode 5 and one or both of the electrodes 3 and 4. v By restricting the area of the discharge passage 10 and using a sufficiently low as pressure referably less than 12 mm. o mercury within the chamber, a brilliant positive column discharge is obtained. This intense light is emitted through the opening 12 in the electrode 5 and through the end of the envelope.

In order to reduce the cathode drop and thus-'still further reduce the starting and operatilg potential of the lamp, the electrodes are coated with an alkali metal, preferably potassium. The potassium 15 may be contained in a side chamber 15 and vaporized onto the electrodes after they are sealed in the envelope.

By having the electrodes 3 and 4 and their leading-in wires entirely enclosed within the chamber 2 and the tubular legs 8, the discharge between these electrodes and the electrode 5, is confined entirely to the restricted portion 10 of the chamber 2 and therefore, there is no stray discharge produced between these electrodes outside of the chamber 2.

In Fig. 2 a modified form of lamp is shown in which the electrodes 16 and 17, adapted to ionize the gas within the tube, are spaced apart longitudinally of the tube so that the discharge therebetween takes place in an axial direction and serves to more eflcientl ionize the gas within the chamber 2. The e ectrode 16 may be in the form of a plate and the electrode 17 a grid or coil spaced thereabove.

The outside electrode 18 is shown in the form of a cylinder or tube surrounding the chamber 2, although it may take the form of a disk, as in Fig. 1 or any other suitable form. That portion of the discharge between the electrode 18 and the open end to the chamber 2, is of insufficient current density to produce light, and a dark spot consequently occurs in this portion of the discharge. Within the oonstricted portion of the chamber, the 'current density is suiciently increased to produce a brilliant positive column. It has been found, however, that the area of the electrode 5 should be greater than the cross sectional area of the constricted portion of the chamber 2 in order to produce such a positive column discharge at commercial voltages.

Fig. 3 shows diagrammatically, one arrangement for operating the lamp in accordance with electrical variations im ressed 0n a circuit in which the lamp is inc uded.`- The electrodes 3 and 4 are connected in circuit with a battery 19, a current varying device 20 and variable resistance 21 and the electrodes 3 and 5 are connected in a local circuit including a battery 22 and the resistance 21. By varying the current in the circuit including electrodes 3 and 4, by means of the current varying device 20, the degree of ionization of the gas in the lamp will be varied and consequently the resistance between the electrodes 3 and 5 increased or decreased to modify the discharge therebetween and cause the light intensity of the positive column discharge to iiuctuate in accordance with the variations produced by the current varying device, which, by way of example, is shown as a microphone.

It has been 'found that a small change inv the ionizing circuit will cause a relatively large change in the light intensity of the lamp. If desired, the current varyino means may be inserted in the circuit includ-ing the electrodes 3 and 5 and the glow-discharge between these electrodes controlled directly in accordance with variations in the current produced thereby.

In Fig. 4 an amplifying tube is introduced between the microphone and the discharge lamp. The ionizing electrodes 3 and 4 are supplied with suitable direct current through the line 23, and the current variations, 1n accordance with which it is desired to control the discharge, are impressed between the electrodes 3 and 5.

The electrode 5 is always at a positive po tential. It is, however, less positive than the electrode 4 and therefore serves as a cathode for the electrode 4 whereby a discharge takes place therebetween, the circuit being completed through the plate and filament of the thermionic amplifier 24 to the Aline 23. The plate 25 of the amplifier is thus also maintained at a positive potential. The electrode 5 is also connected through the current varying device 20 and the battery 26 to the grid d `27 of the amplifier whereby the grid is also given a positive charge. The battery 26, however, is connected in opposition to the line voltage so as to maintain the grid potential slightly lower than the potential of the plate. By thus maintaining t e control circuit including the microphone 20 at a relatively high potential, a large amplification of the variations produced by the microphone is obtained and impressed on the lamp.

lIt is understood, of course, that the microphone 20 has been used as the current varying` devlce only for the sake of simplicity in illus-I dischargelamp in accor ance with current variations transmitted by radio. The receiving apparatus shown in the left of Fig. 5 may be any suitable type, the form here shown being by way of exam le only. The electrical variations received liy the antennae circuit and detected and ampliiied by the thermionic valve 28, are impressed between the electrodes 3 and 5 of the discharge lamp and the intensity of the light is thereby varied in accord-` ance with the received impulses.

` .In Fig. 6'is shown one arrangement for uslng the discharge lamp as a rectifier for supplying direct current, for any desired purpose as, for instance, supplying the plate current for radio tubes. The alternating current source 29, for instance the ordinary commercial lighting circuit of 110 volts, is stepped up by a transformer 30, the opposite ends of which are .connected to the electrodes 3 and 4.

The third electrode in this instance, may take j the form of a plate. 31, which should'be of relatively large area as compared-to the elec-- age may be controlled by a suitable rheostat 36 :The rectification of the alternating current is obtained by virtue ofr the diiference in cathode drop of the electrode 31 and the elec-- trodes 3 and 4. The electrode 31 because of its large surface,has a relatively small cathode drop as compared to the electrodes 3 and 4. It

would. therefore require a higher voltage to i produce ka discharge between either of the electrodes 3 or 4 and the electrode 31 when the former electrodes are .used as a cathode than when the latter is used as a cathode. By suitably proportioning the size and shape of these electrodes and the gas pressure-within the device, the discharge in one direction may be entirely suppressed and a discharge be produced alternately between the electrode 3 and 31 and the electrode 4 and 31.

It will thus be noted that both the positive and negative portions of the alternating current are utilized and a continuous direct current produced.

In place of making the electrodesl 3 and 4 therebetween in one direction only.

It will be understood that this invention is not limited to theparticular embodiments shown and described as many variations may be made in the-construction of the lamp and the circuit connections and apparatus utilized without departing from this invention.

What is claimed is:

1.A discharge lamp comprising an enve-v lope contalmng a rare gas, a pair of closely spaced electrodes within said lamp for reducing the starting potential thereof one of said'electrodes to serve as a main anode and a third .electrode to .serve as a cathode for causing a glow discharge within said lampA and a constricted discharge passage for said discharge.

2. A discharge lamp comprising an envelope having a rare gas therein, a chamber within said envelope having walls .spaced therefrom and having a constricted discharge passage connecting with said envelope, a pair of electrodes in lsaid chamber adapted to have a constant potential impressed thereon to ionize the gas in; said discharge pas sage, and a third electrode outside of said chamber for producing a positive column glow-discharge within s aid constricted passage.

3. A discharge lamp comprising an envelope having a rare gas therein, an open ended chamber within said envelope having impexforatev side-walls spaced therefrom, elec-v trodes spaced longitudinally within said chamber, adapted .to ionize a column of gas therein, and a third electrode outside of said chamber for producing a positive column discharge through the open end of said mem'- ber between said inner and outer electrodes.

4. A discharge device comprising an envelope containing a as, a pair of electrodes of relatively small e ective glow discharge area between which a discharge is adapted to take place to ionize the said gas, a third electrode of greater effective discharge area spaced from said other electrodes and serving as a cathode therefor whereby a positive column glow discharge may be produced between at least one of said other electrodes and said cathode, said third electrode being apertured and means for directing the positive column discharge through the aperture thereof.

5.A discharge lamp comprising an envelope, a reentrant stem, a pair' ofleading-in conductors sealed through said stem, a tubular insulator surrounding both of said leading-in conductors and sealed to said stem, an electrode of small area secured to each of said leading-in conductors and disposed within a tubular insulating member disposed axially of said envelope, said tubular member having a restricted outlet, and a third electrode disposed externally of said tubular member for cooperating with at least one of said first trodes to produce a luminous discharge with-` in said insulating member.

7. A discharge lamp comprising an envelope, a gaseous filling therein, a stem in said envelope, a hollow insulating member within said envelope and sealed at one end'to said stem, an electrode within said hollow member, a leading-in conductor sealed through said stem and joined to said electrode, a tubular discharge passage of small cross section extending from the interior of said hollow member to the exterior thereof, and an electrode disposed externally of said hollow member adjacent said discharge passage to permit light developed in said passage to be viewed along the axis of the assage.

8. A discharge lamp comprlsing an envelope containing a gas at a low pressure, a hollow open-ended insulating member sealed to and forming a chamber within said envelo e, a pair of electrodes, each having small e ective discharge areas, disposed in said chamber for ionizing the gas within said envelope, said hollow member being reduced to form a constricted passage at its open end and a third electrode having a relatively large effective discharge area disposed outside, in alignment with, and adjacent said constricted passage to produce a positive column discharge in said chamber when a variable potential is impressed between the third electrode and at least' one of the ionizing electrodes, said third electrode having an aperture in alignment with said constricted passage.

In testimony whereof, I have hereunto subscribed my name this 8th day of July, 1924.

ERNEST ANTON LEDERER. 

